<!DOCTYPE html>
<html>

<head>
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <title>string对象 </title>
  <script type="text/javascript">
    var message = "I love JavaScript!";
    var mychar = message.toLowerCase();
    document.write("字符串为：" + mychar + "<br>");
  </script>
</head>

<body>
</body>

</html>